Pruning a tree to make it smaller (known as ‘topping’) is ill-advised, particularly on a large growing tree, and should never be done except in rare cases where it is necessary to preserve the tree. Topping a tree causes an immediate serious injury by removing too much live growth, and creates long term health and structural problems. If a tree is in good structural condition it should not need to be made smaller.
An exception is when a tree contains structural defects (splits, cavities, poor unions) that could be corrected by reducing the overall size of the crown. Done correctly, a ‘crown reduction’ type of pruning could add years of life to a valued tree.